> On Aug 5, 2016, at 4:43 AM, Tripoli Massimiliano <m.trip...@aifa.gov.it>
> wrote:
>
> Dear R users,
>
> # This is my data:
>
> ddat <- array(c(8,10,7,13,8,15,
> 7,9,6,9,7,10,
> 11,13,7,16,8,16
> ),
> dim = c(2,3,3),
> dimnames = list(
> Time = c("Week 32","Week 52"),
> Dose = c("Dose 1","Dose 2","Dose 3"),
> Group = c("A","B","C")))
> ddat
>
> # and I'd like to have data like that:
>
> as.data.frame(UCBAdmissions)
>
> # I tried with
>
> as.data.frame(ddat)
>
> # and this is the result:
>
>> as.data.frame(ddat)
> Dose 1.A Dose 2.A Dose 3.A Dose 1.B Dose 2.B Dose 3.B Dose 1.C Dose
> 2.C Dose 3.C
> Week 32 8 7 8 7 6 7 11
> 7 8
> Week 52 10 13 15 9 9 10 13
> 16 16
>
> Someone could help me ?
> Thanks in advance,
>
> M. Tripoli
This has to do with method dispatch.
UCBAdmissions is a table:
> class(UCBAdmissions)
[1] "table"
ddat is an array as you created it:
> class(ddat)
[1] "array"
There is an as.data.frame() method for arrays (as.data.frame.array()) which
results in a flattening of the object and this is defined in ?as.data.frame in
the Details section:
"Arrays can be converted to data frames. One-dimensional arrays are treated
like vectors and two-dimensional arrays like matrices. Arrays with more than
two dimensions are converted to matrices by ‘flattening’ all dimensions after
the first and creating suitable column labels."
In the case of UCBAdmissions, as.data.frame.table() is called yielding the
alternative result that you observe.
If you want to get the same result from ddat, you can either coerce it to a
table first:
> as.data.frame(as.table(ddat))
Time Dose Group Freq
1 Week 32 Dose 1 A 8
2 Week 52 Dose 1 A 10
3 Week 32 Dose 2 A 7
4 Week 52 Dose 2 A 13
5 Week 32 Dose 3 A 8
6 Week 52 Dose 3 A 15
7 Week 32 Dose 1 B 7
8 Week 52 Dose 1 B 9
9 Week 32 Dose 2 B 6
10 Week 52 Dose 2 B 9
11 Week 32 Dose 3 B 7
12 Week 52 Dose 3 B 10
13 Week 32 Dose 1 C 11
14 Week 52 Dose 1 C 13
15 Week 32 Dose 2 C 7
16 Week 52 Dose 2 C 16
17 Week 32 Dose 3 C 8
18 Week 52 Dose 3 C 16
or explicitly call as.data.frame.table():
> as.data.frame.table(ddat)
Time Dose Group Freq
1 Week 32 Dose 1 A 8
2 Week 52 Dose 1 A 10
3 Week 32 Dose 2 A 7
4 Week 52 Dose 2 A 13
5 Week 32 Dose 3 A 8
6 Week 52 Dose 3 A 15
7 Week 32 Dose 1 B 7
8 Week 52 Dose 1 B 9
9 Week 32 Dose 2 B 6
10 Week 52 Dose 2 B 9
11 Week 32 Dose 3 B 7
12 Week 52 Dose 3 B 10
13 Week 32 Dose 1 C 11
14 Week 52 Dose 1 C 13
15 Week 32 Dose 2 C 7
16 Week 52 Dose 2 C 16
17 Week 32 Dose 3 C 8
18 Week 52 Dose 3 C 16
Regards,
Marc Schwartz
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